O/D Off comes on with Brakes

[hwheatthins]

My O/D off turns on and off with every tap of the brake pedal.

I come to a light at 40 mph and as soon as I engage the brakes, the O/D off lights up (and the engine down shifts). At the next light, I engage the brakes again and the O/D light turns off.

It's like i'm pressing the O/D button every time i hit the brakes.

Any ideas??

Edit: 2003 Expedition 5.4

 

[Bedrck47]

care to tell us what year, engine and model your expy is

 

[Stanger4Life]

Year and model would help. My two guesses would be the brake deactivation switch (however that is more so concerning the cruise control, but possibly) my other guess might be a shift solenoid. Do you have any check engine lights or anything? Are you able to scan your computer at all?

 

[hwheatthins]

Sorry! 2003 Expedition 5.4

i'll edit the original post.

 

[hwheatthins]

Year and model would help. My two guesses would be the brake deactivation switch (however that is more so concerning the cruise control, but possibly) my other guess might be a shift solenoid. Do you have any check engine lights or anything? Are you able to scan your computer at all?

no check engine lights at all.

I have an ODB2 scanner i can hook up tonight.

 

[Bedrck47]

also the brake pedal position switch which is different then the deactivation switch

 

[Bedrck47]

rather than edit the original post you can edit your signature by going into the user CP section

 

[Stanger4Life]

also the brake pedal position switch which is different then the deactivation switch

That is also another good idea. Because it only happens when you applying the break, I would imagine it would have to be some sort of electrical component linked to your braking system. Can you make the O/D light turn on and off by applying the brake at idle (in park) or only when it's in drive? Does it come on at any speed or at only certain speeds? If it does it while at idle in park, I might try to disconnect the pedal position switch and or the deactivation switch and see if the problem goes away by pressing the brake at idle, that might be your indication of what part is malfunctioning. Either that or pull out a mulitmeter and check to see if the switches are receiving power. If neither one of those seems to be the issue and no trouble codes, it may be the shift solenoid going out, put I'm thinking the first 2 would be more likely. The brake deactivation switch is pretty common however it is more linked to cruise control problems. I replaced the one in my windstar (it was really obvious) and I might have to change it in my 2005 Expy.

 

[Bedrck47]

The bad thing about disconnecting the brake position switch is it would also affect the brake lights there are two seperate circuits that the switch controls

 

[hwheatthins]

That is also another good idea. Because it only happens when you applying the break, I would imagine it would have to be some sort of electrical component linked to your braking system. Can you make the O/D light turn on and off by applying the brake at idle (in park) or only when it's in drive? Does it come on at any speed or at only certain speeds? If it does it while at idle in park, I might try to disconnect the pedal position switch and or the deactivation switch and see if the problem goes away by pressing the brake at idle, that might be your indication of what part is malfunctioning. Either that or pull out a mulitmeter and check to see if the switches are receiving power. If neither one of those seems to be the issue and no trouble codes, it may be the shift solenoid going out, put I'm thinking the first 2 would be more likely. The brake deactivation switch is pretty common however it is more linked to cruise control problems. I replaced the one in my windstar (it was really obvious) and I might have to change it in my 2005 Expy.

It comes on ANYTIME i tap the brakes regardless of whether or not it's in park.

I think it's definitely an electrical problem.

How would I go about trouble shooting with the multimeter? Which components should i test?

 

[Bedrck47]

can you read and understand electrical diagrams

 

[hwheatthins]

can you read and understand electrical diagrams

haha somewhat. Took a few electronics and physics classes in high school about ten years ago.

 

[stamp11127]

If the overdrive light comes on when you press the brake but goes off when you release the brakes, you have power being fed from the brake circuit to the portion of the overdrive cancel switch (as Ford calls it) between the switch and the pcm, or the switch is stuck closed and power can be at any point.
The first wire to look at is a tan & white stripe wire. When power is applied to this wire the pcm turns off the overdrive.

 

[Bedrck47]

attached are the prints you should need to check the Brake Pedal Position Switch

You need to check for continuity between pins 1 and 2 , 5 and 6

or to test for voltage at pin 2 and ground
and pin and ground for 12 Volts

If you look at print 90-04 you will see the switch and the power comes from fuse F1.5 and goes thru the switch it then goes to the, ABS control
module and the Brake shift interlock on the expedition. There is a splice in the line going to those components which could be part of the problem

 

[hwheatthins]

If the overdrive light comes on when you press the brake but goes off when you release the brakes, you have power being fed from the brake circuit to the portion of the overdrive cancel switch (as Ford calls it) between the switch and the pcm, or the switch is stuck closed and power can be at any point.
The first wire to look at is a tan & white stripe wire. When power is applied to this wire the pcm turns off the overdrive.

hmmm

It's like this...

Tap and release brakes --> O/D off

Top and release brakes --> O/D on

 

[Bedrck47]

print for O/D switch

 

[stamp11127]

Ok, I'll admit I had to look at the symbol legend to make sure, the switch may be a momentary on switch instead of a two position switch. That would make sense of why it toggles on/off with each brake application.

 

[stamp11127]

OP - see if lowering the steering column has any effect.

 

[metaldrgn]

Like Stamp said, it sounds like wires have chaffed or been damaged and the brake switch and O/D switch wiring are shorted causing it to behave that way. If you get continuity where you shouldn't you've found your shorted wires then you just need to find/repair them.

One thing I've found in some of my cars including my expedition is either an anti-theft addon or a vehicle disabling system for dealers to ensure they get their payments or your car would be disabled. The wiring jobs for them are pretty crappy and I've noticed some bare wire on both. I don't know why they would tap into those wires, but they could have by accident. Those units are usually located under the drivers side dash around the steering column.

 

[hwheatthins]

Sincerely appreciate the advice and feedback, everyone. I will try all of this tonight and will report back!

Plugged in OBD2 scanner and it returned zero codes